1 . ANALYSIS OF THE OLDEST SEDIMENTARY ROCKS PROVIDES

EVIDENCE FOR THE ORIGIN OF LIFE

Life on Earth

Questions

  What were the conditions on early Earth?   What are the two scientific theories relating to the

evolution of the chemicals of life?   What are some of the changes in technology that

have assisted in increasing our understanding of the origin of life?

Technology

 Dot Point – Identify changes in technology that have assisted in the development of an increased understanding about the origin of life and the evolution of living thing

Technology

Technologies enabled the testing of hypotheses being proposed by scientists: Early Technologies: •  Swan-necked flasks designed by Louis Pasteur – showed that air alone could not trigger spontaneous generation of microorganisms • The light microscope 1676 – Microorganisms discovered using the light microscope More Recent Technologies: •  Radiometric dating e.g. radiocarbon dating – allowed scientists to assign absolute dates to the sequence of life on Earth – used to establish geological timescales and thus fossils and rates of evolutionary change •  Study of meteorites and volcanoes •  Study of plate tectonics through rock dating – Continental drift and sea floor spreading • Simulation of conditions of early Earth

Organic chemicals essential for life

  There is evidence that life existed on Earth 3.8 billion years ago, and this was only possible because of the presence of water.

  Essential elements necessary for life to form include hydrogen, oxygen, carbon, nitrogen, phosphorous, and sulfur.

  Living organisms use energy from sunlight or from chemical reactions to combine these in various ways to form their organic molecules – carbohydrates, proteins, lipids (fats) and nucleic acids.

The Primitive atmosphere

  It is very difficult to recreate the conditions that would have been present on the Earth at the time of its formation.

  Scientists have tried, through experiments, to create the conditions that prevailed at the time.

  There are currently two main views on where life developed on the early Earth:  Chemosynthetic – living matter is produced from non-

living matter  Panspermia- organic molecules

carried to earth via meteorite •  Scientists still argue about

the source of life.

Haldane and Oparin

  In the 1920s, John Haldane, a scottish biochemist and Alexander Oparin, a Russian scientist independently hypothesised that organic molecules would be spontaneously produced when an energy source, such as UV light or lightening, interacted with the (non-living) elements essential to life.

The Experiments of Urey and Miller

The Experiments of Urey and Miller

  1953 – Stanley Miller and Harold Urey tested Oparin and Haldane’s hypotheses.

  They set up glass apparatus as shown in the previous slide.

 To simulate the Earth’s atmosphere, the gases of water vapour, methane, hydrogen and ammonia were mixed and exposed constantly to an electric spark, which mimicked lightening.

 During this time a flask of water that represented the ocean was heated, water vapour was given off and later passed through a condenser as recycled liquid water (rain).

The Experiments of Urey and Miller

  http://www.youtube.com/watch?v=iahBQolXQH8

The Experiments of Urey and Miller

  After one week of treatment the liquid in the flask was red and cloudy.

  When tested, it was found to contain amino acids – the basic unit of proteins – which are made up of carbon, oxygen, hydrogen and nitrogen, as well as other organic molecules.

  Amino acids are one common need of all living things – they are the building blocks of proteins

Research Activity

  Dot Point – Gather information from secondary sources to describe the experiments of Urey and Miller and use the available evidence to analyse the:

  Reason for their experiments   Result of their experiments   Importance of their experiments in illustrating the nature and

practice of science   Contribution to hypotheses about the origin of life

*Analyse - Identify components and the relationship between them; draw out and relate implications*

Research Activity

  Visit the Urey and Miller Experiment class wiki at:

https://ureyandmillerexperiment.wikispaces.com/home

1.  Work in pairs with someone you wouldn’t normally work with. Upload your information to share with the class – do not copy and paste slabs of information. Make concise summaries of your research to share with the class

2.  Present your findings to the class

Further experiments

  More recent experiments have tested a range of atmospheres and used different energy sources that could have existed on Earth.

  The successful production of all of Earth’s 20 amino acids from these experiments, and also of lipids, sugars and nucleic acids indicate that the organic molecules necessary for life could have been built under primitive anoxic conditions, consistent with that of early Earth, with the aid of an available energy source such as volcanic heat, solar radiation, UV light or electricity.

Significance of the experiments

  Why are the experiments of Urey and Miller significant in the debate on the composition of the primitive atmosphere?

Significance of the experiments

  Dot Point – discuss the significance of the Urey and Miller experiments in the debate on the composition of the primitive atmosphere

  The experiment is of tremendous importance in the quest for the truth about the origin of life because it demonstrated that organic molecules could be manufactured from inorganic molecules under conditions thought to mirror those 3.8 billion years ago.

  Effectively, Urey and Miller’s experiment supported Oparin and Haldane’s hypothesis that life originated on Earth due to the presence of local inorganic chemicals and an energy source.

  Some scientists saw this as debunking the outer space theory, while others still pursue the outer space theory today.